WHY SPENT FILTER BACKWASH WATER RECOVERY?

There is increasing interest in recovering spent filter backwash water.

Economics

One reason is that spent filter backwash water represents a large volume of water with low solids content. Recovering this water can result in a savings in water resources and the chemicals originally used to pre-treat it.

Regulatory Compliance

Another reason for recovering spent filter backwash water is regulatory. Many regulatory agencies prohibit the discharge of water plant wastes into the environment or have waste handling procedures that are costly.

THE RISK OF SPENT FILTER BACKWASH WATER RECOVERY

Increased Concentrations of Pathogens

While the practice of recycling spent filter backwash water has long been regarded as acceptable, it is generally stored in lagoons or ponds and then returned to the head of the plant with little or no further treatment. This can increase the risk of re-introducing increased concentrations of pathogenic contaminants such as Giardia and Cryptosporidium to the filters and filtered water.

Controlling the Risk

By treating recovered filter backwash water before re-introducing it to the filter, this risk can be controlled. In fact, in the U.S., the Filter Backwash Recycling Rule will soon come into effect. The purpose of the Rule is to prevent the concentrated pathogenic contaminants potentially in the spend filter backwash water from being returned to the head of the water treatment plant without some form of treatment or dilution.

The risk of re-introducing concentrations of pathogens to the filter and filtered water can be effectively controlled by further removing the solids to which the pathogenic contaminants can attach.

See also:
Backwash Water Recovery, Leopold System Solutions.